Question
Factorise the following:$(2a - b)^2 -9(3c - d)^2$
✓
Answer
$(2a - b)^2 - 9(3c - d)^2$
$= (2a - b)^2 - [3(3c - d)]^2$
$= [(2a - b) - 3(3c - d)][(2a - b) + 3(3c - d)]$
$= (2a - b - 9c + 3d)(2a - b + 9c - 3d).$
$= (2a - b)^2 - [3(3c - d)]^2$
$= [(2a - b) - 3(3c - d)][(2a - b) + 3(3c - d)]$
$= (2a - b - 9c + 3d)(2a - b + 9c - 3d).$
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